Bedbugger: News reports about the research indicate the possibility that bed bugs are spreading or have spread in the past via chickens from breeder houses to poultry workers and to the community, is that correct? How significant a factor could this be in the bed bug resurgence in this country and others? And do New Yorkers, who live in a city of seventy or more viveros need to be concerned that urban live poultry markets may also be a conduit, not just via chickens but also via the business next door (structurally, the markets can be in the ground level of apartment buildings) and its employees and even customers?

James Austin: Yes, we have found significant populations of bed bugs in poultry facilities and given their unique ability to phoretically transfer (hitching rides on other organisms), bed bugs are very likely using alternate hosts (such as chickens) to fulfill their dietary needs. This could be a significant factor in the resurgence of bed bugs globally…not just in the USA. To suggest that all bed bug occurrences have emanated from international travel is unrealistic. There are undoubtedly endemic occurrences that are contributing to the resurgence phenomenon.

As for New Yorkers being concerned about live chicken markets…I would be concerned. You have to put bed bug history into context here. Likely, bed bugs were first associated with bats, moved onto humans that probably dwelled in caves, and then onto poultry. When you look at other Cimicids there is a significant number that have direct relationships to various domestic and wild birds, so it isn’t a stretch to see how bed bugs have utilized chickens (and other galliformes) as their food source.

Bedbugger: You have isolated human DNA from bed bugs. Do bed bugs have the potential of becoming a common and significant forensic indicator? Have they already been used in criminal cases?

James Austin: Bed bugs have tremendous potential for assisting forensic experts in criminal investigations, because unlike other obligate blood feeders both male and female bugs must consume a blood meal prior to molting. Bed bugs won’t stray too far away from their hosts if they are consistently available. This means that if you wanted to link a suspect in a criminal investigation to an exact location, you could get pretty darn close. Besides demonstrating that the recovery of human blood from bed bugs is possible, we have also conducted time course analyses and have demonstrated that we can recover mitochondrial DNA (mtDNA) up to 7 days after feeding and short tandem repeat DNA (or STRs) up to 60 days. This offers a significant time window of opportunity for forensic investigators to possibly recover blood samples from bugs that were in proximity to a location of interest. There were no specific differences between male and females in terms of recovering human DNA. To our knowledge, there has not been a criminal investigation where human DNA recovered from bed bugs has been used, but this offers another view to forensic experts if all the right pieces of the jigsaw puzzle are there.

Bedbugger: What is the relevance of genetic population studies of bed bugs to the issues of pesticide resistance and what are the findings so far?

James Austin: If you contextualize genetics and resistance together an alarming (and not too unfamiliar) picture emerges. Based on our use of both mtDNA and nuclear DNA (nDNA) we find significant variation without population structure and support recency of the whole resurgence phenomenon. In other words, we genetically demonstrate no variation in nDNA (which supports recency of resurgence scenarios) and the lack of population structure with mtDNA suggests rapid movement of populations. Basically, this research supports what a lot of researchers believed was true without supporting it empirically.

Bedbugger: We want to make sure we understand the findings. You tested samples from chicken breeding facilities and also from field collections elsewhere in the U.S., is that correct? The genetic variation and population structure you found point to a) populations of bed bugs surviving over a continuous period (presumably on alternate hosts like the poor chickens), and b) a recent expansion of these bed bug populations. Or can we speak of a single, genetically simple population of bed bugs?

James Austin: Yes…we looked at populations collected from numerous locations in addition to poultry facilities. We employed two classes of genetic markers, mtDNA and nDNA. mtDNA provides a glimpse at the maternal lineage of any successive population since this is maternally inherited. nDNA share both parental contributions so you can at least get some perspective of the paternal input as well. In most cases it encodes more of the genome than the mtDNA and is passed sexually rather than matrilineally. Both genes can coevolve within the same populations at different rates. It takes significantly longer to observe changes in nDNA sequences than in mtDNA sequences.

By applying both to these disjunct populations, we are able to definitely support that bed bug resurgence is more recent (if there was significant variation here you would imply that change was going on and continued to go on for some time) and that the absence of population structure from mtDNA sequences supports large scale mixing of populations (if populations were isolated, you would likely detect geographic correlations with where certain haplotypes (of mtDNA) occur). I think it would be too simplistic to believe that all our bed bug problems originated from a single founding population. If this were so, you would have essentially no mtDNA variation because they would all be related. No…in this case there have been several points of origination and likely mixing of several populations which have culminated into the situation we have at hand.

Bedbugger: And the U.S. bed bug population genetic picture with regard to pesticide resistance? What is a “genetic bottleneck” and what are the implications?

James Austin: While screening multiple populations of bed bugs against various insecticides we have found virtually all populations were 100% resistant to DDT. This is not a surprise given that the first observances of DDT resistance were noted almost 50 years ago. It is a little surprising that they continue to be so completely resistant to DDT. This fact would support a “genetic bottleneck” where DDT susceptible populations were so aggressively challenged to DDT that it wiped them all out…only the highly resistant populations might have survived (a bottleneck), hence the relative freedom we have had from bed bugs for so many years. There are examples from other organisms that demonstrate cross resistance from one insecticide to another insecticide (largely because they have similar modes of action), but this doesn’t seem to be as common in bed bugs that we have evaluated from poultry facilities. Without doubt, we find resistant populations that have been challenged with organophosphates (OPs) and the like, so it is too early to assume anything yet. The bottom line here is that when it comes to treating bed bug infestations, careful lessons learned from cockroach management apply (rotate chemicals, good sanitation, applying push and pull techniques, etc.).

Bedbugger: But that is a tall order when it comes to bed bugs, isn’t it? Rotating chemical classes and push-pull (which, and please correct us if we’re wrong, we understand is a strategy to move insects towards treated surfaces via the use of attractants) is going to be hard because, well, we got nothing at present. Or is there hope in any of these areas? Can their aggregating habits favoring feces-marked locations be turned against them?

James Austin: You are correct in that the strategy of push-pull applications focuses movement to a desired area. However, it doesn’t necessarily mean towards a treated area. It is relatively clear that bed bugs favor warm foci for obvious reasons (if you are an obligate blood feeder, you can only find blood from a warm blooded animal…heat=possible meal). Push and pull techniques might employ non-repellent chemistries and heated target zones (or possibly traps). There is good evidence that bed bugs do prefer harboring in areas where feces is deposited. Studies on C. lectularius and other cimicids appear consistent in that they prefer these areas. Your last inquiry about turning their preferred roosting areas against them is one that you will see a lot more of in the near future.

Bedbugger: Can we hope that bed bugs will one day have the research footprint of termites or other economically important pests?

James Austin: In the short run they very well may already have that footprint. One of the reasons termites get people’s ire up so much is the thought of an unseen invader eating one of their most valued possessions, their home. Like termites, nothing would get my ire up a lot more than being fed on while I sleep or thinking about them on my children. This will take a little time, but I think there will be significant interest in bed bug research in the years to come.

Bedbugger: We want to end with a thought about the chickens. What is being done to alleviate their condition? It pains us to think of chickens suffering bed bug bites. Are current control methods having an effect?

James Austin: Unfortunately, no. Many large-scale poultry producers do not even have entomologists on staff to consider ways to manage resistance in these insects. Until producers change their ways, they are more likely to contribute to the problem than assist with correcting it. Now, to be fair to them, it isn’t their fault either. These insects have been around many, many years and they are doing what they do best, surviving at all costs. So, we needn’t be too alarmed that this has occurred, but we can’t just sit on our duffs hoping for better days either.

Heartfelt thanks to Dr. Austin for his generosity and this wonderful discussion.

Update 9/09/08: North Carolina State University researchers have been awarded a USDA-NRI grant to, ambitiously, use bed bug population genetics to determine the source and movement of bed bugs, within buildings, cities and surrounding areas, and even between countries… and between poultry farms/urban environments, to determine whether poultry farms are important sources of the spread. We look forward to hearing more from the researchers on the project, Warren Booth, Ed Vargo, and Coby Schal.

so i wonder if it would be too much to establish a link between the resurgence in bedbugs and the massive growth in poultry farming in the states since the 1990s? forgive me if this has been theorized already, i just find it interesting.

also, more directly relating to the interview, i’m absolutely fascinated by the idea of using bedbugs in forensic cases. this had not even occured to me as a possibility! my understanding of dna is limited at best, but if they can extract DNA from a bedbug 60 days after feeding, what implications does this have (if any) for the current bedbug status as non-vectors of disease potentially changing?

Terrific interview. It may go over the heads of many, but one item people will notice — DDT is not the silver bullet. Hopeless, you can apparently create a highly effective trap (push-pull) with glue pads and hand warmers — according to an entomologist cited on this very blog.

Thanks, Nomo
I have been looking forward to hearing more about the results of Dr. Austin’s research.

Finding that 100% of the bed bug specimens from disjoint populations were resistant to DDT confirms the view that DDT was a primary factor in the near eradication of bed bugs from households in the US sixty years ago. This revelation should also help settle the debate about the merits of bringing DDT back to the marketplace

I wonder if we could use Bed Bug Dogs and DNA markers to trace the migration path of bed bugs from the poultry facilities into our urban areas. I would love to participate in that kind of research.

Establishing the role of poultry operations in the resurgence of bed bugs globally suggests that another important vector (chicken farming) should be targeted for pest control.

I happen to agree with you lieutenantdan, how exactly does a mass migration of bed bugs go from chicken coups to homes? It’s not like all of us are chicken breeders.

I think it’s reasonable to think that a large population of bed bugs, or cimicids (have they been id’d to be lectularis?), have been present in chicken breeding/harvesting facilities for many years, but how does that contribute to a resurgence in human population? Could a few farmers take a few back to their houses, sure, start the whole worldwide firestorm, I doubt it.

Then again, if I missed something, someone please clue me in.

Either way, great interview and article. It’s fun to see some hardcore science on the site.

I was actually looking for some other information and took a moment to read some of the chatter about this interview and thought to add a short comment. For clarification…bed bugs likely use other passeriformes (wild indigenous birds such as sparrows, starlings, robins, etc.) as either intermediate hosts when galliformes (chickens and turkeys) are unavailable (removed from poultry houses for production and meat harvesting), and they are phoretically transferred from nests (on birds) adjacent to or residing on poultry facilities (to other locations)…a common occurrence and entirely validated by the observance of bed bugs in their respective nests and our investigations using genera specific molecular markers. You have to remember that the poultry facilities in question are for the growth of meat, where chickens reside for significant times without movement out of the houses (often in excess of 230 days). When they (the wild birds) fly to urban areas or make nests on homes and apartments they accidentally transfer bed bugs to these locations. This has been demonstrated with many cimicid species around the world (on bats too!) including eagles and other falconiformes. It would take considerable time to develop large populations after a sweeping application of DDT followed by various synthetic organic insecticides that followed, especially the organochlorines. The identity of these bugs, like all the other studies mentioned, were corroborated morphologically and genetically leaving no doubt about what insects we are talking about here. I hope this clears up some of your confusion. BTW…researchers in Europe get most if not all of their bed bugs for research from the same types of poultry facilities in eastern Europe and the Middle East, so this problem is not unique to the USA. I hope this helps inform you more.

North Carolina State University researchers Ed Vargo and Coby Schal have been awarded a USDA-NRI grant to, ambitiously, use bed bug population genetics to determine the source and movement of bed bugs, within buildings, cities and surrounding areas, and even between countries… and between poultry farms/urban environments, to determine whether poultry farms are important sources of the spread.

The work at NC state also involved myself. Unfortunately due to University regulations post-docs (despite writing the grant) are not allowed to be listed as a co-PI on the grant.
I am the post-doc working directly on the project.